Berkeley landscape architect Peter Walker has designed bigger projects than the 9/11 memorial in New York, but probably none has carried more weight. The opening of the eight-acre plaza Sunday marks 10 years since the terrorist attacks, and almost as many years since Walker joined with architect Michael Arad to finalize a monument for ground zero. The design -- down to plaza lights like the model Walker is holding -- demanded as much attention to emotion as to aesthetics and engineering. With work on One World Trade Center and the museum still in progress, it is the memorial that will first meet the public eye and, if it succeeds, affix in the public heart the harrowing sorrow and transcendent memory of 9/11 for as long as such monuments endure.

On this project you have about 350 million clients: the American people.

That's right, and of completely different points of view. Even [among] the families, the interests are not all the same. One hopes the memorial itself will bring a certain closure to the families and maybe even pull them together.

Architect Michael Arad's "Reflecting Absence" was one of eight finalists in the design competition. At the jury's suggestion, he asked you to partner with him. What did the design have to accomplish?

There were two different points of view being expressed. One was the need that New York has for the memorial and rebuilding. But they didn't want a field of stone. They wanted it to operate as a neighborhood park as well as a memorial.

[Then-Gov. George] Pataki had a good handle on [it]. He said: "We're memorializing what happened because we don't want to forget it. But we're also memorializing the ability of New York to rebuild, and so you've got to have both the tragedy and the response."

You've said this undertaking has been like Hemingway's "The Old Man and the Sea" -- you caught this huge fish, now, how do you get it home with any meat left on it?

Our part is almost the same as the original conception. Michael's has changed radically, and it's been difficult on him. When we began, you went down ramps into the "underworld" and you saw the [victims'] names and then waterfalls behind them. About two years into the effort, it was [changed] for financial reasons, but mostly security.

The memorial probably is as big a target as the [towers] were, and much more easily destroyed. The security people said that halfway down the ramp, you'd have [a checkpoint] like at the airport. Everyone felt that would pretty much destroy your sense of going down into this tomb. So they decided to get rid of the lower portion.

We [Walker and his firm] lost a few things, but we also won some real battles. When we started, the [site's] below-ground [structures] needed vents, and because of security, these vents had to be 25 feet tall. Imagine, 16 vents coming up in the middle of [the memorial.] We made a model -- we called it the Awful Model -- and we took it to Gov. Pataki. He got it immediately. He turned to the engineers and said: "We can't have any of this. Absolutely none." [Now] the buildings on the west side have those vents.

Walk me through what a visitor will see.

Before, it was largely a processional down into a tomb. [Now you] walk onto the block, come through and under the trees, and then come onto the voids [two deep waterfalls in the footprints of the twin towers, with the names of the victims etched on the perimeter]. The sun comes in. And we have a recessional as well. The trees are an expression of life when you turn and walk out.

What is the cost of the entire ground zero rebuilding project?

They won't tell us. But the memorial is a very small part, maybe 10%. The museum and the Freedom Tower have to make money because we need a cash flow to keep this operating.

With memorials there's a tension between the abstract and the literal.

There are memorials that have no real quality, and there are the great ones, like the Lincoln and the Vietnam. You try to catch that abstract thing, and if you do, I think you succeed. If you can't, it becomes nondescript, like the Korean War [memorial]; you probably can't even picture it. I can't picture it. It doesn't have that weight.

If the emotion comes through [at the 9/11 memorial], and the scale is right, those are terribly important, more important than the trees individually, more important than benches, right up there with the names themselves.

The design was slammed by some critics; the New York Post said it stunk.

People I respect -- not necessarily the Post -- Ada Louise Huxtable said it was too large, which is a valid criticism. But the critical thing happens and then goes away. What's important for me first is, what do the families think? And then, what does the public think? The measure is, are they going to come? And I think they are. The event was so vivid -- in some ways more vivid than wars because wars are removed. [The memorial] is not so different from a Holocaust museum, even though it's completely different in purpose; but it's about memory and understanding and keeping that alive.

Is it possible that some monuments, even perhaps this one, get built too soon?

That's a possibility. I was on the National Endowment for the Arts panel that went to Oklahoma City after the bombing, and people told us what they thought. The reactions [were] so diverse and so emotional, our committee thought it would be difficult for a designer to grasp them. We recommended they wait two or three years. But they wanted something now.

[Franklin] Roosevelt was a case in point. He wanted a piece of stone about the size of his desk with his name on it. The family wanted that, and it was [built]. But by the time the Roosevelt Memorial was built, it was mythic. Larry [designer Lawrence Halprin] said: "Look, my client wasn"t the Roosevelt family. It was the people coming to see this."

The 400-plus white swamp oak trees destined for the site remind me of sacred groves of antiquity.

[People] used to hold religious ceremonies in forests, and the oaks were the tallest trees. There was a mystical thing about oak trees; they've been used ever since in memorials.

New York is tough on trees. The average tree in New York lives seven to 10 years. It would be terrible if in 10 years the [memorial's] trees started dying. So we used a tree that was not immediately known to have these [stresses].

We did a tremendous amount to make the site hospitable to trees. Instead of putting them in boxes, we put them in long trenches to have roots out feeding and taking in air. We put in a system which catches snow and rainwater, and then you pump that water back up for irrigation.

Remember, 500 reasonably mature trees -- there's no nursery that has 500 trees. We traveled all over to find them. We took [them] to New Jersey, so they could acclimate. We got them all into the same size and almost perfect. Most people would think they were perfect.

We had this idea that where people stand and read the [victims'] names each September, that it would be wonderful to have a tree that would color up and have that brilliance at just about that time. Liquidambar does that. Michael's been very tense about this; he's felt that any competition to [the display of names] was a danger to success. He didn't want anything theatrical, and we didn't either.

And what about the waterfall fountains in the two voids that rest in the footprints of the twin towers?

These fountains are gigantic -- 200 feet on a side, that's 1,600 feet [total]. I've done a lot of waterfalls; you'd have to put an inch or inch and a half of water across the weir [a device that guides the water over the edge]. That's a colossal amount of water. You're not using any energy when it falls, but then you have to pump it back up so it can fall over and over again. A wonderful designer in Toronto discovered a way of reducing that by about 70%, which over the years in the electric bills is going to make a huge difference.

In the design process, did you talk to the families and look at artifacts?

Yeah. It's really upsetting. They have a warehouse full. It takes your breath away. And then you go into the family room at the Lower Manhattan Development Corp.; it was full of teddy bears and notes from 5-year-olds and pictures. It really is tough. [Some families] had gotten themselves together; some had not. They are helpful, they are difficult, they are everything.

Will we know by looking at the memorial that it's your design?

You won't. Landscape architects will because we are noted for certain things. We do very restrained, very minimal, in some ways very simple but in some ways intellectually complex things. I work with architects, and if you think about it, architecture mostly is about verticality. [Buildings] are sort of phallic. And landscape -- my metaphor, the horizontal -- represents the Earth.

Michael Arad and you bested more than 5,000 entries. What went through your mind when you got that call?

I was shocked, although I had no reason at that moment to know how shocked I should have been. You're delighted and suddenly your whole world changes. Suddenly they're calling press conferences; suddenly youre on every morning television show. I've never had a client as complicated as this, so it really did change my life.

Did people send you their own ideas?

Oh yes. I heard from many, many people, and often they're basically telling you their idea is better than yours.

What is your 9/11 story? Where were you?

I was in San Francisco; my wife was in Muncie and called and said, "Turn on the TV." That wasn't the moment. The moment that hit me hardest -- I was in Macy's trying on some pants. This was three years [later], and [outside the dressing rooms] they were watching loops of the event [on TV] , and I'm just buying pants, right? And I realize, we're in the middle of something.

Two waterfall voids mark the location of the former twin towers and form the centerpiece of a memorial plaza at the World Trade Center site. New high-rise construction continues on two sides of the plaza.

Hilda Solis brought to D.C. a no-bones-about-it track record from the California Legislature, where she raised the minimum wage, raised the bar for worker protections and raised some hell for environmental laws.

Daughter of legendary county Supervisor Kenneth Hahn, sister of former Mayor James Hahn, the Democrat won the special election to replace Jane Harman in the coastal/South Bay 36th Congressional District.